It is known to remove starch and starch-containing sizing materials from textile substrates by impregnating sized fabric with enzyme solutions which decompose starch, the treatment being carried out under conditions suitable for cleavage of the starch sizing to water-soluble cleavage products and subsequent removal of the decomposition products of the starch sizing by a washing process. As starch-decomposing enzymes, one can use amylases from malt and pancreas or from mold or bacteria cultures.
It is known further to cultivate, by appropriate adaptation and selection of amylase-producing bacteria, strains which are characterized by high temperature-insensibility and stability. Amylases from cultures of these strains can also be used at temperatures of 100.degree. C. and higher as desizing agents. They are known as high-temperature amylases (G. B. Madsen, B. E. Norman, S. Slott: "Die Starke", 25, 304 (1973)).
For conducting the desizing, especially for the better wetting of the textile material with the desizing solution, it is also known to add wetting agents to the desizing bath (German Pat. No. 849,987; German Auslegeschriften Nos. 1,135,857 and 1,041,468; "Process Biochemistry 5" (1970) 8,17-19; "Melliand Textilberichte", 1970,1060-1062). Such wetting agents promote the absorption capacity of the fabric but display, more often than not, enzyme-inhibiting or enzyme-injuring action. The wetting agents are, therefore, always first brought into contact with the enzyme in the desizing bath when it is not possible, through certain combinations, to prepare free flowing pulverulent compositions (German Pat. No. 849,987; German Auslegeschrift No. 1,041,468). Most surfactants, especially the anionic surfactants, as, for example, sulfonic acids, are, however, inhibitors of enzyme action and strong enzyme poisons which cannot be used even for a short time in the desizing bath. In general, non-ionic surfactants inhibit the desizing enzymes less than anionic surfactants.